Graduate School of Materials Science, Nara Institute of Science and Technology (NAIST), 8916-5 Takayama, Ikoma, Nara 630-0192, Japan.
Chemistry. 2011 Sep 19;17(39):10951-7. doi: 10.1002/chem.201101495.
The photochromic reactivity of terarylenes is integrated with molecular folding that is controlled through a host-guest interaction. A thieno[3,2,b]pyridine unit is introduced into a photochromic terarylene structure as an aryl unit to form a guest-interacting site. Thienopyridine-containing terarylenes showed solvent-dependent photochromic reactivity in solution. A terarylene moiety that contains two thienopyridyl units showed significantly high photocoloration reactivity as high as 88% of photocyclization quantum yield in methanol, whereas that value was only 24% in hexane. A temperature-dependent (1)H NMR spectroscopic study in different solvents indicated an interconversion between photochromic-reactive and unreactive conformations. In methanol, the intermolecular interaction between terarylene species and the solvent molecule slows the rate of interconversion and increases the population of the photochromic-active form, whereas the unreactive conformation is dominant in hexane. Crystal-structural studies demonstrated the perfect regulation of molecular folding between a photochromic-active form and an unreactive conformation by changing the solvents for recrystallization. Single crystals prepared from solutions in methanol showed reversible photochromic reactivity, whereas recrystallization from solutions in hexane did not show this reactivity. X-ray crystallographic studies of single crystals from solutions in methanol demonstrated that the photochromic molecules bind a solvent methanol molecule at the guest-interacting site to regulate the molecular conformation into a photochromic-active form in collaboration with specific intramolecular interactions, whereas crystals from solutions in hexane possess the photochromic-unreactive conformation.
将三芳基乙烯的光致变色反应与通过主体-客体相互作用控制的分子折叠相结合。噻吩并[3,2-b]吡啶单元被引入光致变色三芳基乙烯结构中作为芳基单元，以形成客体相互作用位点。含噻吩吡啶的三芳基乙烯在溶液中表现出溶剂依赖性光致变色反应。含有两个噻吩吡啶单元的三芳基乙烯部分显示出非常高的光致变色反应活性，高达 88%的光环化量子产率在甲醇中，而在正己烷中仅为 24%。在不同溶剂中进行的温度依赖性（1）H NMR 光谱研究表明，光致变色反应性和非反应性构象之间存在相互转化。在甲醇中，三芳基乙烯物种与溶剂分子之间的分子间相互作用会减缓相互转化的速度，并增加光致变色活性形式的比例，而在正己烷中则以非反应性构象为主。晶体结构研究表明，通过改变重结晶用溶剂，可以完美地调节光致变色活性形式和非活性构象之间的分子折叠。从甲醇溶液中制备的单晶显示出可逆的光致变色反应性，而从正己烷溶液中重结晶则没有表现出这种反应性。甲醇溶液单晶的 X 射线晶体学研究表明，光致变色分子在客体相互作用位点结合一个溶剂甲醇分子，以协同特定的分子内相互作用将分子构象调节为光致变色活性形式，而正己烷溶液中的晶体则具有光致变色非活性构象。
